The present invention relates to methods and compositions for enhancing diffusion of therapeutic agents, such as gene therapy vectors, through tissue. Also, the present invention relates to methods and compositions for selectively destroying tissue.
There are numerous applications in which a therapeutic agent is delivered to a tissue of interest. For example, gene therapy, in which the therapeutic agent comprises a vector carrying a polynucleotide, involves the introduction of DNA or RNA into one or more mammalian cells and/or tissues. Gene therapy holds great promise as a clinical treatment for a variety of human maladies, including various cancers, and many different therapeutic strategies have been devised. Examples of such strategies include replacement of an aberrant gene that caused cells to become malignant and inducement of tumor cells to manufacture a toxic substance that ultimately kills them.
A vector of some type is typically used to deliver the polynucleotide to the cells or tissue being treated. Viral vectors are currently the most frequently used vector in gene therapy procedures. Many different types of viruses can be used as the vector, with adenovirus and retrovirus being among the most commonly used.
In order for gene therapy to be successful, the vector must be delivered to the target tissue and successfully introduce the polynucleotide into the cells. Lastly, the genetic material carried by the vector must be ultimately located in the nucleus or other compartment of the host cell such that the polynucleotide, commonly referred to as a transgene or transgenes, can be expressed.
Frequently, delivery of the vector to the tissue of interest presents a significant challenge. The use of common systemic delivery methods, such as intravenous injection, is unattractive because it is typically desired to limit introduction of the transgene to a specific tissue. Furthermore, the transgene may produce a toxic substance. Thus, it is advantageous to limit exposure to the transgene to the tissue of interest. A simple approach to achieving this limited exposure has been to inject the viral vectors directly into the tissue of interest, usually a tumor or other diseased tissue. While this direct delivery does limit exposure of other tissues to the transgene, it also limits distribution of the transgene within the targeted tissue. Following injection, the majority of the injected vector load remains in the cells near the path created by the injection device. As a result, the volume of tissue that can be infected, and therefore treated, is restricted by the limited distance that the vector can diffuse through the intercellular space of the tissue.
The present invention provides methods of enhancing the diffusion of a therapeutic agent through tissue. A method in accordance with the present invention comprises delivering a permeabilizer to the tissue of interest. The permeabilizer is one or more member of a family of macrocyclic compounds previously used to enhance the rate at which a drug crosses skin membranes of various body cavities, the blood-brain barrier, and similar macroscopic membranes. This family of compounds is described in detail in U.S. Pat. No. 5,023,252 to Hsieh for TRANSDERMAL AND TRANS-MEMBRANE DELIVERY OF DRUGS, which is hereby incorporated by reference in its entirety. In preferred methods and compositions, the permeabilizers are one or more of cyclopentadecanone, cyclopentadecanolide, ethylene brassylate, or civetone. The permeabilizer may be administered prior to, concurrently with, or subsequent to delivery of the therapeutic agent to the tissue.
Methods according to the present invention may further include inducing hyperthermia in the tissue of interest. Preferably, inducing hyperthermia comprises elevating the temperature of the tissue and maintaining an elevated temperature for a period of time prior to, during, and/or following delivery of the agent to the tissue. Alternatively, acute hyperthermia may be employed.
In one aspect, the invention provides a method of enhancing the diffusion of a gene therapy vector through mammalian tissue. A preferred method according to this aspect of the invention comprises inducing hyperthermia in the tissue, delivering a permeabilizer to the tissue, and delivering the gene therapy vector to the tissue. Preferably, the permeabilizer and vector are delivered together.
The permeabilizer and hyperthermia act to increase the intercellular space of the tissue. At certain concentrations and temperatures, the process that increases the intercellular space is sufficient to effectively destroy the tissue. Thus, the present invention also provides a method of selectively destroying tissue. A preferred method according to this aspect of the invention comprises delivering a particular concentration of a permeabilizer to the tissue while inducing hyperthermia in the tissue and then maintaining hyperthermia.
In a further embodiment, the present invention provides a composition useful for performing in vivo, in vitro, or in situ gene therapy procedures in a tissue of interest. A preferred composition according to this aspect of the invention comprises an effective amount of the gene therapy vector that includes polynucleotide and an effective amount of a permeabilizer. The composition can be used with the methods of the present invention for performing gene therapy procedures.